The ranges and abundances of species that depend on freshwater habitats are declining worldwide. Efforts to counteract those trends are often hampered by a lack of information about species distribution and conservation status and are often strongly biased toward a few well-studied groups.We identified the 3,906 vascular plants, macroinvertebrates, and vertebrates native to California, USA, that depend on fresh water for at least one stage of their life history. We evaluated the conservation status for these taxa using existing government and non-governmental organization assessments (e.g., endangered species act, NatureServe), created a spatial database of locality observations or distribution information from ∼400 data sources, and mapped patterns of richness, endemism, and vulnerability. Although nearly half of all taxa with conservation status (n = 1,939) are vulnerable to extinction, only 114 (6%) of those vulnerable taxa have a legal mandate for protection in the form of formal inclusion on a state or federal endangered species list. Endemic taxa are at greater risk than non-endemics, with 90% of the 927 endemic taxa vulnerable to extinction. Records with spatial data were available for a total of 2,276 species (61%). The patterns of species richness differ depending on the taxonomic group analyzed, but are similar across taxonomic level. No particular taxonomic group represents an umbrella for all species, but hotspots of high richness for listed species cover 40% of the hotspots for all other species and 58% of the hotspots for vulnerable freshwater species. By mapping freshwater species hotspots we show locations that represent the top priority for conservation action in the state. This study identifies opportunities to fill gaps in the evaluation of conservation status for freshwater taxa in California, to address the lack of occurrence information for nearly 40% of freshwater taxa and nearly 40% of watersheds in the state, and to implement adequate protections for freshwater taxa where they are currently lacking.

Assessing habitat quality to identify the highest priority sites for conservation planning is a complex task, and requires an understanding of which habitat attributes are most important for species population success. I explored the relative importance of biotic, abiotic, spatial, or disturbance-related habitat attributes to the population abundance of four edaphic-endemic, disturbance-dependent rare plant species. Variable selection provided a way to evaluate the relative importance of ecologically relevant groups of habitat attributes. Overall, biotic and disturbance history variables were the best predictors of population abundance for all four gabbro rare plant species, while spatial and abiotic variables were not found to be strong drivers of population abundance. Habitat quality for the four rare plants evaluated here may be best characterized by the associated species in the vegetation community, and an appropriate disturbance regime is a key component to maintain populations over time.